DOCX Input: Add support for EMF images

DOCX Input: Add support for embedded EMF images that are just wrappers
around an actual raster image. See #1224849 (DOCX to EPUB conversion failed with devide by zero)
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Show full path of library in status bar

Show full path of library under mouse in status bar when
switching/renaming/deleting libraries via the calibre library button.
Fixes #1224925 [[Enhancement]Show full path for libraries](https://bugs.launchpad.net/calibre/+bug/1224925)
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Ignore errors in third party UI plugins during genesis
Comments editor: Allow treating arbitrary URLs as images

Merge branch 'master' of https://github.com/cbhaley/calibre
Have metadata.book.set_all_user_metadata actually set the metadata, not merge it.